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• Anomalie #3320 : Personnalisation du tri des articles dans l’espace privé par _TRI_ARTICLES_RUBRIQUE

  31 octobre 2014, par Julien PORIAU

  b b a écrit :

  Super, merci grand :)

  Yes. Merci bien !

• Anomalie #3351 (Fermé) : Le header ’link’ est affiché dans la page généré au lieu d’être envoyé pa...

  23 novembre 2014, par marcimat ☺☮☯♫

  Bon, en fait c’était déjà résolu par spip:r21816
  Bizarrement tout n’était pas à jour dans mon test.
  Super.
  Merci :)

• libavcodec : how to encode with h264 codec ,with mp4 container using controllable frame rate and bitrate(through c code)

  26 mai 2016, par musimbate

  I am trying to record the screen of a pc and encode the recorded frames using h264 encoder
  and wrap them into a mp4 container.I want to do this because this super user link http://superuser.com/questions/300897/what-is-a-codec-e-g-divx-and-how-does-it-differ-from-a-file-format-e-g-mp/300997#300997 suggests it allows good trade-off between size and quality of the output file.

  The application I am working on should allow users to record a few hours of video and have the minimum output file size with decent quality.

  The code I have cooked up so far allows me to record and save .mpg(container) files with the mpeg1video encoder

  Running :

  ffmpeg -i test.mpg

  on the output file gives the following output :

   [mpegvideo @ 028c7400] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, mpegvideo, from 'test.mpg':
  
    Duration: 00:00:00.29, bitrate: 104857 kb/s
  
      Stream #0:0: Video: mpeg1video, yuv420p(tv), 1366x768 [SAR 1:1 DAR 683:384], 104857 kb/s, 25 fps, 25 tbr, 1200k tbn, 25 tbc

  I have these settings for my output :

   const char * filename="test.mpg";
  
      int codec_id= AV_CODEC_ID_MPEG1VIDEO;
  
      AVCodec *codec11;
  
      AVCodecContext *outContext= NULL;
  
      int got_output;
  
      FILE *f;
  
      AVPacket pkt;
  
      uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  
  
      /* put sample parameters */
  
      outContext->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
      outContext->width=pCodecCtx->width;
  
      outContext->height=pCodecCtx->height;
  
      /* frames per second */
  
      outContext->time_base.num=1;
  
      outContext->time_base.den=25;
  
      /* emit one intra frame every ten frames
  
       * check frame pict_type before passing frame
  
       * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
  
       * then gop_size is ignored and the output of encoder
  
       * will always be I frame irrespective to gop_size
  
       */
  
      outContext->gop_size = 10;
  
      outContext->max_b_frames = 1;
  
      outContext->pix_fmt = AV_PIX_FMT_YUV420P;

  When I change int codec_id= AV_CODEC_ID_MPEG1VIDEO to int codec_id= AV_CODEC_ID_H264 i get a file that does not play with vlc.

  I have read that writing the

  uint8_t endcode[] = { 0, 0, 1, 0xb7 };

  array at the end of your file when finished encoding makes your file a legitimate mpeg file.It is written like this :

   fwrite(endcode, 1, sizeof(endcode), f);
  
      fclose(f);

  in my code. Should I do the same thing when I change my encoder to AV_CODEC_ID_H264 ?

  I am capturing using gdi input like this :

  AVDictionary* options = NULL;
  
      //Set some options
  
      //grabbing frame rate
  
      av_dict_set(&options,"framerate","30",0);
  
      AVInputFormat *ifmt=av_find_input_format("gdigrab");
  
      if(avformat_open_input(&pFormatCtx,"desktop",ifmt,&options)!=0){
  
          printf("Couldn't open input stream.\n");
  
          return -1;
  
          }

  I want to be able to modify my grabbing rate to optimize for the outptut file size
  but When I change it to 20 for example I get a video that plays so fast.How do
  I get a video that plays with normal speed with frames captured at 20 fps or any
  lower frame rate value ?

  While recording I get the following output on the standard error output :

  [gdigrab @ 00cdb8e0] Capturing whole desktop as 1366x768x32 at (0,0)
  
  Input #0, gdigrab, from '(null)':
  
    Duration: N/A, start: 1420718663.655713, bitrate: 1006131 kb/s
  
      Stream #0:0: Video: bmp, bgra, 1366x768, 1006131 kb/s, 29.97 tbr, 1000k tbn, 29.97 tbc
  
  [swscaler @ 00d24120] Warning: data is not aligned! This can lead to a speedloss
  
  [mpeg1video @ 00cdd160] AVFrame.format is not set
  
  [mpeg1video @ 00cdd160] AVFrame.width or height is not set
  
  [mpeg1video @ 00cdd160] AVFrame.format is not set
  
  [mpeg1video @ 00cdd160] AVFrame.width or height is not set
  
  [mpeg1video @ 00cdd160] AVFrame.format is not set

  How do I get rid of this error in my code ?

  In summary :
  1) How do I encode h264 video wrapped into mp4 container ?

  2) How do I capture at lower frame rates and still play
  the encoded video at normal speed ?

  3) How do I set the format(and which format—depends on the codec ?)
  and width and height info on the frames I write ?

  The code I am using in its entirety is shown below

  extern "C"
  
  {
  
  #include "libavcodec/avcodec.h"
  
  #include "libavformat/avformat.h"
  
  #include "libswscale/swscale.h"
  
  #include "libavdevice/avdevice.h"
  
  
  
  
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavutil></libavutil>channel_layout.h>
  
  #include <libavutil></libavutil>common.h>
  
  #include <libavutil></libavutil>imgutils.h>
  
  #include <libavutil></libavutil>mathematics.h>
  
  #include <libavutil></libavutil>samplefmt.h>
  
  //SDL
  
  #include "SDL.h"
  
  #include "SDL_thread.h"
  
  }
  
  
  
  //Output YUV420P
  
  #define OUTPUT_YUV420P 0
  
  //'1' Use Dshow
  
  //'0' Use GDIgrab
  
  #define USE_DSHOW 0
  
  
  
  int main(int argc, char* argv[])
  
  {
  
  
  
      //1.WE HAVE THE FORMAT CONTEXT
  
      //THIS IS FROM THE DESKTOP GRAB STREAM.
  
      AVFormatContext *pFormatCtx;
  
      int             i, videoindex;
  
      AVCodecContext  *pCodecCtx;
  
      AVCodec         *pCodec;
  
  
  
      av_register_all();
  
      avformat_network_init();
  
  
  
      //ASSIGN STH TO THE FORMAT CONTEXT.
  
      pFormatCtx = avformat_alloc_context();
  
  
  
      //Register Device
  
      avdevice_register_all();
  
      //Windows
  
  #ifdef _WIN32
  
  #if USE_DSHOW
  
      //Use dshow
  
      //
  
      //Need to Install screen-capture-recorder
  
      //screen-capture-recorder
  
      //Website: http://sourceforge.net/projects/screencapturer/
  
      //
  
      AVInputFormat *ifmt=av_find_input_format("dshow");
  
      //if(avformat_open_input(&amp;pFormatCtx,"video=screen-capture-recorder",ifmt,NULL)!=0){
  
      if(avformat_open_input(&amp;pFormatCtx,"video=UScreenCapture",ifmt,NULL)!=0){
  
          printf("Couldn't open input stream.\n");
  
          return -1;
  
      }
  
  #else
  
      //Use gdigrab
  
      AVDictionary* options = NULL;
  
      //Set some options
  
      //grabbing frame rate
  
      av_dict_set(&amp;options,"framerate","30",0);
  
      //The distance from the left edge of the screen or desktop
  
      //av_dict_set(&amp;options,"offset_x","20",0);
  
      //The distance from the top edge of the screen or desktop
  
      //av_dict_set(&amp;options,"offset_y","40",0);
  
      //Video frame size. The default is to capture the full screen
  
      //av_dict_set(&amp;options,"video_size","640x480",0);
  
      AVInputFormat *ifmt=av_find_input_format("gdigrab");
  
      if(avformat_open_input(&amp;pFormatCtx,"desktop",ifmt,&amp;options)!=0){
  
          printf("Couldn't open input stream.\n");
  
          return -1;
  
      }
  
  
  
  #endif
  
  #endif//FOR THE WIN32 THING.
  
  
  
      if(avformat_find_stream_info(pFormatCtx,NULL)&lt;0)
  
      {
  
          printf("Couldn't find stream information.\n");
  
          return -1;
  
      }
  
      videoindex=-1;
  
      for(i=0; inb_streams; i++)
  
          if(pFormatCtx->streams[i]->codec->codec_type
  
                  ==AVMEDIA_TYPE_VIDEO)
  
          {
  
              videoindex=i;
  
              break;
  
          }
  
      if(videoindex==-1)
  
      {
  
          printf("Didn't find a video stream.\n");
  
          return -1;
  
      }
  
      pCodecCtx=pFormatCtx->streams[videoindex]->codec;
  
      pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
  
      if(pCodec==NULL)
  
      {
  
          printf("Codec not found.\n");
  
          return -1;
  
      }
  
      if(avcodec_open2(pCodecCtx, pCodec,NULL)&lt;0)
  
      {
  
          printf("Could not open codec.\n");
  
          return -1;
  
      }
  
  
  
      //THIS IS WHERE YOU CONTROL THE FORMAT(THROUGH FRAMES).
  
      AVFrame *pFrame;
  
  
  
      pFrame=av_frame_alloc();
  
  
  
      int ret, got_picture;
  
  
  
      AVPacket *packet=(AVPacket *)av_malloc(sizeof(AVPacket));
  
  
  
      //TRY TO INIT THE PACKET HERE
  
       av_init_packet(packet);
  
  
  
  
  
      //Output Information-----------------------------
  
      printf("File Information---------------------\n");
  
      av_dump_format(pFormatCtx,0,NULL,0);
  
      printf("-------------------------------------------------\n");
  
  
  
  
  
  //&lt;&lt;--FOR WRITING MPG FILES
  
      //&lt;&lt;--START:PREPARE TO WRITE YOUR MPG FILE.
  
  
  
      const char * filename="test.mpg";
  
      int codec_id= AV_CODEC_ID_MPEG1VIDEO;
  
  
  
  
  
  
  
      AVCodec *codec11;
  
      AVCodecContext *outContext= NULL;
  
      int got_output;
  
      FILE *f;
  
      AVPacket pkt;
  
      uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  
  
      printf("Encode video file %s\n", filename);
  
  
  
      /* find the mpeg1 video encoder */
  
      codec11 = avcodec_find_encoder((AVCodecID)codec_id);
  
      if (!codec11) {
  
          fprintf(stderr, "Codec not found\n");
  
          exit(1);
  
      }
  
  
  
      outContext = avcodec_alloc_context3(codec11);
  
      if (!outContext) {
  
          fprintf(stderr, "Could not allocate video codec context\n");
  
          exit(1);
  
      }
  
  
  
      /* put sample parameters */
  
      outContext->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
  
  
      outContext->width=pCodecCtx->width;
  
      outContext->height=pCodecCtx->height;
  
  
  
  
  
      /* frames per second */
  
      outContext->time_base.num=1;
  
      outContext->time_base.den=25;
  
  
  
      /* emit one intra frame every ten frames
  
       * check frame pict_type before passing frame
  
       * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
  
       * then gop_size is ignored and the output of encoder
  
       * will always be I frame irrespective to gop_size
  
       */
  
      outContext->gop_size = 10;
  
      outContext->max_b_frames = 1;
  
      outContext->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      if (codec_id == AV_CODEC_ID_H264)
  
          av_opt_set(outContext->priv_data, "preset", "slow", 0);
  
  
  
      /* open it */
  
      if (avcodec_open2(outContext, codec11, NULL) &lt; 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      f = fopen(filename, "wb");
  
      if (!f) {
  
          fprintf(stderr, "Could not open %s\n", filename);
  
          exit(1);
  
      }
  
  
  
  
  
      AVFrame *outframe = av_frame_alloc();
  
      int nbytes = avpicture_get_size(outContext->pix_fmt,
  
                                     outContext->width,
  
                                     outContext->height);
  
  
  
      uint8_t* outbuffer = (uint8_t*)av_malloc(nbytes);
  
  
  
     //ASSOCIATE THE FRAME TO THE ALLOCATED BUFFER.
  
      avpicture_fill((AVPicture*)outframe, outbuffer,
  
                     AV_PIX_FMT_YUV420P,
  
                     outContext->width, outContext->height);
  
  
  
      SwsContext* swsCtx_ ;
  
      swsCtx_= sws_getContext(pCodecCtx->width,
  
                              pCodecCtx->height,
  
                              pCodecCtx->pix_fmt,
  
                              outContext->width, outContext->height,
  
                              outContext->pix_fmt,
  
                              SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
  
  
      //HERE WE START PULLING PACKETS FROM THE SPECIFIED FORMAT CONTEXT.
  
      while(av_read_frame(pFormatCtx, packet)>=0)
  
      {
  
          if(packet->stream_index==videoindex)
  
          {
  
              ret= avcodec_decode_video2(pCodecCtx,
  
                                           pFrame,
  
                                           &amp;got_picture,packet );
  
              if(ret &lt; 0)
  
              {
  
                  printf("Decode Error.\n");
  
                  return -1;
  
              }
  
              if(got_picture)
  
              {
  
  
  
              sws_scale(swsCtx_, pFrame->data, pFrame->linesize,
  
                    0, pCodecCtx->height, outframe->data,
  
                    outframe->linesize);
  
  
  
  
  
              av_init_packet(&amp;pkt);
  
              pkt.data = NULL;    // packet data will be allocated by the encoder
  
              pkt.size = 0;
  
  
  
  
  
              ret = avcodec_encode_video2(outContext, &amp;pkt, outframe, &amp;got_output);
  
              if (ret &lt; 0) {
  
                 fprintf(stderr, "Error encoding frame\n");
  
                 exit(1);
  
                }
  
  
  
              if (got_output) {
  
                  printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
                  fwrite(pkt.data, 1, pkt.size, f);
  
                  av_free_packet(&amp;pkt);
  
                 }
  
  
  
              }
  
          }
  
  
  
          av_free_packet(packet);
  
      }//THE LOOP TO PULL PACKETS FROM THE FORMAT CONTEXT ENDS HERE.
  
  
  
  
  
  
  
      //
  
      /* get the delayed frames */
  
      for (got_output = 1; got_output; i++) {
  
          //fflush(stdout);
  
  
  
          ret = avcodec_encode_video2(outContext, &amp;pkt, NULL, &amp;got_output);
  
          if (ret &lt; 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
  
  
          if (got_output) {
  
              printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
              fwrite(pkt.data, 1, pkt.size, f);
  
              av_free_packet(&amp;pkt);
  
          }
  
      }
  
  
  
  
  
  
  
      /* add sequence end code to have a real mpeg file */
  
      fwrite(endcode, 1, sizeof(endcode), f);
  
      fclose(f);
  
  
  
      avcodec_close(outContext);
  
      av_free(outContext);
  
      //av_freep(&amp;frame->data[0]);
  
      //av_frame_free(&amp;frame);
  
  
  
      //THIS WAS ADDED LATER
  
      av_free(outbuffer);
  
  
  
      avcodec_close(pCodecCtx);
  
      avformat_close_input(&amp;pFormatCtx);
  
  
  
      return 0;
  
  }

  Thank you for your time.